Gripping apparatuses for gripping and holding elongated workpieces, such as lines, pipes, bars, flexible lines, or the like, are used in a multiplicity of technical machines, by which they are processed in one way or another. In particular, such gripping apparatuses can be found, for example, in bending machines, such as wire-bending machines or pipe-bending machines, where they are used for both seizing a workpiece at a specific location (for example, in a magazine, at a conveyor belt or at a processing station) and then transferring it, for example, to a subsequent station (processing station or depositing belt), as well as for guiding a received workpiece to a processing position, holding it during processing and then passing it on, if necessary, to a subsequent discharge position.
In this case, a multiplicity of grippers are generally provided for inserting, depositing, transporting and fixing the workpieces in a single pipe- or wire-bending machine, one or several of these grippers serving mainly, for example, to fix the workpieces during processing and others, in the form of movable auxiliary grippers, serving to stabilize the workpiece during bending and to fetch new workpieces from the magazine. In many cases, the gripping apparatuses are located on a pivotable gripper arm, are mounted, in particular as auxiliary grippers, also such that they are movable on the base frame, and comprise a housing carrying two gripping jaws, which are movable between an opened receiving position and a closed clamping position (for receiving the workpiece).
DE 3620151 A1 discloses the use of a central holding and gripping apparatus in the form of a clamping chuck, by which the received workpiece can also be rotated about its longitudinal axis, in a machine for bending rod-shaped workpieces. If required, a second gripping apparatus may be employed, or the gripping apparatus may be attached to a robot. However, these gripping apparatuses are relatively big and bulky. The design of the clamping chuck is not explained in detail in said reference.
DE 39 22 326 C2 as well as EP 0 934 783 B1 describe gripping apparatuses which are respectively provided as simple, cylinder-operated lever mechanisms, with the respective cylinder being located directly at the gripping apparatus, so that the total mass of the latter is again relatively large.
The gripping apparatuses of DE 601 00 147 T2 are each provided with two gripping jaws executing a linear gripping movement for seizing and clamping the workpiece to be received. However, this reference does not explain the gripping movement in detail.
DE 603 01 913 T2 discloses the attachment of gripping apparatuses to a portal. In this case, the gripping apparatuses are located on gripper arms which can be pivoted about an axis that is parallel to the axis of the workpiece to be received; the gripping movement is effected via cylinders or a motor. However, there is no detailed explanation of the gripping apparatuses themselves in this reference.
DE 196 30 023 A1 describes a rotary gripping apparatus which is equipped with gripping jaws that are respectively pivotable about an axis of rotation. Said gripping jaws engage with each other via teeth and are pivoted to their respective clamping positions by two cylinders. However, this known gripping assembly has a construction which requires a considerable amount of space, and the gripping apparatus is attached to a circular ring, so that the free bending space is also limited.
Finally, a gripping apparatus of the type mentioned above is known from DE 20 2004 011 947 U1. This gripping apparatus is movable on the machine bed, but this reference does not provide any more detailed information on the specific design of the gripping apparatus itself.